Exhaust-gas turbocharger

ABSTRACT

An exhaust-gas turbocharger includes an outer housing, a bearing flange connected to the outer housing by a material joint, and a turbine wheel rotatable about a rotation axis. Formfittingly connected to the bearing flange is an inner housing which is formed with a collar having at least one section in contact with an inner edge of the bearing flange in a direction of the rotation axis of the turbine wheel.

CROSS-REFERENCES TO RELATED APPLICATIONS

This application claims the priority of German Patent Application,Serial No. 10 2010 021 114.1-13, filed May 20, 2010, pursuant to 35U.S.C. 119(a)-(d), the content of which is incorporated herein byreference in its entirety as if fully set forth herein.

BACKGROUND OF THE INVENTION

The present invention relates to an exhaust-gas turbocharger.

The following discussion of related art is provided to assist the readerin understanding the advantages of the invention, and is not to beconstrued as an admission that this related art is prior art to thisinvention.

Internal combustion engines in particular for motor vehicles areincreasingly charged by fluid flow machines to further improveefficiency and thereby reduce fuel consumption. An example of a fluidflow machine is a turbocharger. The turbocharger and especially theturbocharger housing should be accurately suited to the powercharacteristic of the engine at hand. In order for the turbocharger tooperate at high efficiency, gap dimensions have to be maintained before,during, and after operation. Temperature differences of up to several100° C. are encountered between various operating conditions, causingthe various structural parts and used materials as well as materialthicknesses to undergo expansions which deviate from one another. In theevent of an expansion, gap dimensions change so that the presence of anunwanted blow-by within the turbocharger may be encountered. Thisadversely affects efficiency. In addition, components may come intocontact with one another as a result of different expansions. In theworst case scenario, components collide, causing damage or a totalbreakdown of the turbocharger.

Another important factor in automobile construction relates to weightwhich should be reduced for all materials and components. Manufacturersstrive therefore to optimize weight for a turbocharger, in particular ofthe turbocharger housing in sheet-metal construction.

German Pat. No. DE 100 22 052 A1 proposes a decoupling ofexhaust-conducting components and supporting and sealing outerstructures. While the exhaust-conducting components of a turbochargerare exposed to high thermal stress and thus glow during operation, thethermal stress on the sealing outer structure is markedly less. However,also the outer housing is subject to very high thermal stress andflow-based stress especially in the regions of attachment onto thebearing housing of a turbocharger and also at the inflow sides of therelatively hot exhausts.

The outer housing of an exhaust-gas turbocharger is normally made ofunshaped sheet-metal shells which are typically welded by thermaljoining with the bearing flanges. Also coupled with the bearing flangesis an inner housing of the exhaust-gas turbocharger. The inner housingnormally rests against the bearing flanges or is additionally coupledwith the bearing flanges by a material joint. When the inner housingrests upon the bearing flanges, different thermal expansion coefficientsmay cause leakage and thus may cause a blow-by. When implementing acoupling through a material joint, the heat impact zone of the thermaljoining process is weakened in terms of geometry and material as aconsequence of the thermal joining process. This region may thusencounter fatigue fracture and even crack formation under extreme stressconditions.

It would therefore be desirable and advantageous to provide an improvedexhaust-gas turbocharger to obviate prior art shortcomings.

SUMMARY OF THE INVENTION

According to one aspect of the present invention, an exhaust-gasturbocharger includes an outer housing, a bearing flange connected tothe outer housing by a material joint, a turbine wheel rotatable about arotation axis, and an inner housing formfittingly connected to thebearing flange and formed with a collar which has at least one sectionin contact with an inner edge of the bearing flange in a direction ofthe rotation axis of the turbine wheel.

The term “collar”, as used in the specification relates to a projectionwhich represents a circular section in the inner housing. The collarpoints hereby with its projection in the direction of the rotation axisof the turbine wheel. A coupling of the inner housing with the bearingflange via the collar and the inner edge refers in particular to aconfiguration of the collar as facing away from an interior space of theinner housing so as to be able to contact the edge of the bearingflange. This is beneficial because the inner housing can be positionedin radial and axial directions in an optimum manner so that rubbing orcontact of the turbine housing is prevented during operation.

A formfitting coupling is ensured by a contact between inner housing andthe bearing flange in at least one section via the collar and the edge.This formfitting coupling further compensates the required manufacturingtolerances as encountered during the production process of theexhaust-gas turbocharger. A turbocharger with optimized gap width canthus be realized by a coupling in accordance with the invention.

According to another advantageous feature of the present invention, thecollar has a bearing-flange-proximal end and is defined by a diameterwhich may increase in a direction toward the bearing-flange-proximalend. Thus, the diameter of the collar increases in the direction of thebearing flange to be coupled with the inner housing. As a result, thecollar receives a bulged configuration. This enhances flow dynamics andthe bulged or flared configuration causes an even and/or reduced stresspattern in the collar.

According to another advantageous feature of the present invention, thecollar and the edge may touch one another in a formfitting manner sothat the collar is arranged with an undercut in relation to the edge. Asthe diameter of the bearing-flange-proximal end of the collar increases,the presence of a formfitting seat between the collar and the edge isestablished. The collar engages behind the edge so as to establish alocking function or a fit. The establishment of a particularly firm seatbetween inner housing and bearing flange is an important aspect of thepresent invention.

According to another advantageous feature of the present invention, thecollar has in a transition zone between the inner housing and the collara foot region which is defined by a bending radius. Currently preferredis a configuration of the collar in the form of a collared hole. Thecollared hole extends from the inner housing and includes in relation tothe inner housing a foot region in which the collar merges in asubstantially funnel-shaped and/or cylinder-shaped collar portion. Thefoot region can be defined by a bending radius which does notnecessarily have to be constant but may vary about the rotationmovement. As a result, the foot region in particular, i.e. thetransition between inner housing and collar, provides the turbochargerwith a beneficial stress pattern.

According to another advantageous feature of the present invention, theedge may have a geometry which is complementary to a geometry of thebending radius of the foot region. The edge and the collar thus bearupon one another at least in one area to further promote an advantageousformfitting coupling. This is beneficial in particular when positioningthe inner housing in radial and axial directions and in terms of adimensional precision of the inner housing during operation of theturbocharger.

According to another advantageous feature of the present invention, thecollar and the edge touch one another with flat contact at least in onearea of the bending radius of the foot region. This has a positiveeffect on the operation of the turbocharger. Any encountered expansionsof components and resultant stress are thus streamlined in such a way asto establish a firm and tight seat between inner housing and bearingflange during the entire operation in the absence of critical stresspeaks.

According to another advantageous feature of the present invention, thecollar and the edge may touch one another with flat contact in thedirection of the rotation axis of the turbine wheel at least in onecontact area which is oriented in the direction of the rotation axis ofthe turbine wheel. This results in a length in which the collar of theinner housing flatly contacts the edge of the bearing flange. Thecentral orientation axis of the contact area extends hereby orientedessentially in the direction of the rotation axis of the turbine wheel.This is beneficial because of the presence of elastic reserves of theinner housing and the collar. Stress caused by different thermalexpansions of components can be dispersed in particular in the contactarea in the direction of the rotation axis of the turbine wheel tothereby extend the life of a turbocharger according to the invention.

According to another advantageous feature of the present invention, theinner housing may be made of two half-shells, with one of thehalf-shells facing the bearing flange and having an S-shapedconfiguration. The collar may be a component of an end portion of theS-shaped configuration. This reduces costs for manufacturing thehalf-shell. As a result of the S-shaped configuration, the half-shellcan be manufactured in one operating step in a forming tool. Moreover,again any stress encountered in the inner housing and also between theinner housing and the outer housing can be advantageously compensated ina spring-like manner by the S-shaped configuration. As a result, theinner housing can expand in relation to the outer housing withoutadversely affecting the efficiency or the operation of the exhaust-gasturbocharger.

According to another advantageous feature of the present invention, theinner housing can have a wall thickness of less than 1.5 mm. Currentlypreferred is a wall thickness of less than 1 mm. As a result of thecoupling of the inner housing with the bearing flange in accordance withthe present invention, the wall thickness for the inner housing can beselected very small. Thus, there is less residual stress within theinner housing and there is less heat introduction into the inner housingespecially during assembly when compared to a great wall thickness. Theexhaust-gas turbocharger can therefore be brought more rapidly tooperating temperature and thus operates in an optimum efficiency range.Furthermore, the overall system of the internal combustion engine andalso the exhaust-gas aftertreatment can be brought more rapidly tooperating temperature so that the starting behavior of for example acatalytic converter produces less emission during the start-up phase.

According to another advantageous feature of the present invention, thecollar and the edge may be coupled with one another by a material joint.Currently preferred is a coupling of the collar and the edge by a radialcircumferential weld seam. To further reinforce the coupling betweeninner housing and bearing flange, the formfitting connection may besupplemented by a material joint. This has a positive effect on the lifeof the connection as well as on the tightness of the connection.

According to another advantageous feature of the present invention, thecollar can engage behind the edge and can be coupled with the edgethrough thermal joining in a circumferential joining zone at abearing-flange-proximal end of the collar. This prevents the weld seamfrom direct exposure to the flow of hot exhaust gas. A weakening in thisregion as a result of heat impact by the thermal joining process and thepresence of the weld seam is of no consequence as this region is notdirectly exposed to the flow of hot and highly corrosive exhaust gas.Again, this extends the life of an exhaust-gas turbocharger according tothe invention.

BRIEF DESCRIPTION OF THE DRAWING

Other features and advantages of the present invention will be morereadily apparent upon reading the following description of currentlypreferred exemplified embodiments of the invention with reference to theaccompanying drawing, in which:

FIG. 1 is a sectional view of an exhaust-gas turbocharger according tothe present invention; and

FIG. 2 shows an enlarged detailed view of coupling in an area betweenbearing flange and inner housing.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

Throughout all the figures, same or corresponding elements may generallybe indicated by same reference numerals. These depicted embodiments areto be understood as illustrative of the invention and not as limiting inany way. It should also be understood that the figures are notnecessarily to scale and that the embodiments are sometimes illustratedby graphic symbols, phantom lines, diagrammatic representations andfragmentary views. In certain instances, details which are not necessaryfor an understanding of the present invention or which render otherdetails difficult to perceive may have been omitted.

Turning now to the drawing, and in particular to FIG. 1, there is showna sectional view of an exhaust-gas turbocharger according to the presentinvention, generally designated by reference numeral 1. The exhaust-gasturbocharger 1 includes an outer housing 2 and an inner housing 3arranged in the outer housing 2. Both the outer housing 2 and the innerhousing 3 are each made of two half-shells, with the outer housing 2comprised of a left half-shell 4 and a right half-shell 5 as relating tothe drawing plane, and the inner housing 3 comprised of a lefthalf-shell 6 and a right half-shell 7.

The half-shells 4, 5, 6, 7 have each a substantial S-shapedconfiguration. At their respective coupling zones, the half-shells 6, 7of the inner housing 3 and the half-shells 4, 5 of the outer housing 3overlap one another, as indicated by reference numeral 8 by way ofexample. The overlap 8 is configured in such a way that the righthalf-shells 5, 6 overlap the left half-shells 4, 6, respectively.Furthermore, the half-shells 4, 5, 6, 7 are coupled to one another by amaterial joint in the form of a circumferential weld seam 9 The innerhousing 3 is arranged on the left-hand side in relation to the drawingplane within the outer housing 2 with a sliding seat 10.

Accommodated in the inner housing 3 is a turbine wheel 11 which issupported within the exhaust-gas turbocharger 1 by a turbine wheel shaft12, only indicated here. The turbine wheel shaft 12 is thusdeterminative for the rotation axis 13 of the turbine wheel 11. Theouter housing 2 is coupled on the right-hand side as relating to thedrawing plane with a bearing flange 14. The coupling is realized by aformfit in a contact zone 15 and by a material joint in the form of acircumferential weld seam 9. The bearing flange 14 is further providedwith an inner edge 16. The edge 16 defines an opening O within thebearing flange 14. The opening O is traversed by a collar 17 of theinner housing 3 so that the collar 17 is able to contact upon the edge16. The collar 17 is defined by an internal diameter DI and an outerdiameter DA which increases in the direction of the bearing flange 14.The collar 17 thus engages behind or is arranged in undercuttingrelationship to the bearing flange 14 in the area of the edge 16 toestablish a firm formfitting engagement. The presence of acircumferential weld seam 18 further reinforces the fixed positioningbetween the collar 17 and the edge 16.

FIG. 2 shows an enlarged detailed view of coupling in an area betweenthe collar 17 of the inner housing 3 and the edge 16 of the bearingflange 14. In the exemplary embodiment shown here, the edge 16 isillustrated with a bending radius R which extends in the direction ofthe bearing flange 14. The bending radius R may be variable depending onthe function and thus need not be defined as a constant. The collar 17has a foot region 19 which corresponds to the contour of the bendingradius R so as to establish a substantially flat contact.

The collar 17 and the edge 16 are also in substantial flat contact in acontact area 20, with the contact surface having a center axis 21 whichis oriented substantially in the direction of the rotation axis 13 (notshown here) of the turbine wheel 11. The inner housing 3 has a wallthickness W which is less than 1.5 mm. Currently preferred is a wallthickness of less than 1 mm. A relief clearance 22 is provided betweenthe bearing flange 14 and the inner housing 3 to ensure a reliable seatof the inner housing 3 upon the bearing flange 14 and a good tightnessin the presence of thermal expansions.

While the invention has been illustrated and described in connectionwith currently preferred embodiments shown and described in detail, itis not intended to be limited to the details shown since variousmodifications and structural changes may be made without departing inany way from the spirit and scope of the present invention. Theembodiments were chosen and described in order to explain the principlesof the invention and practical application to thereby enable a personskilled in the art to best utilize the invention and various embodimentswith various modifications as are suited to the particular usecontemplated.

1. An exhaust-gas turbocharger, comprising: an outer housing; a bearingflange connected to the outer housing by a material joint; a turbinewheel rotatable about a rotation axis; and an inner housingformfittingly connected to the bearing flange and formed with a collarwhich has at least one section in contact with an inner edge of thebearing flange in a direction of the rotation axis of the turbine wheel.2. The exhaust-gas turbocharger of claim 1, wherein the collar has abearing-flange-proximal end and is defined by a diameter which increasesin a direction toward the bearing-flange-proximal end.
 3. Theexhaust-gas turbocharger of claim 1, wherein the collar and the edgetouch one another in a formfitting manner so that the collar is arrangedin undercutting relationship to the edge.
 4. The exhaust-gasturbocharger of claim 1, wherein the collar has in a transition zonebetween the inner housing and the collar a foot region which is definedby a bending radius.
 5. The exhaust-gas turbocharger of claim 4, whereinthe edge has a geometry which is complementary to a geometry of thebending radius of the foot region.
 6. The exhaust-gas turbocharger ofclaim 5, wherein the collar and the edge touch one another with flatcontact at least in an area of the bending radius of the foot region. 7.The exhaust-gas turbocharger of claim 1, wherein the collar and the edgeflatly touch one another in the direction of the rotation axis of theturbine wheel at least in one contact area which is oriented in thedirection of the rotation axis of the turbine wheel.
 8. The exhaust-gasturbocharger of claim 1, wherein the inner housing is made of twohalf-shells, with one of the half-shells facing the bearing flange andhaving an S-shaped configuration.
 9. The exhaust-gas turbocharger ofclaim 1, wherein the inner housing has a wall thickness of less than 1.5mm.
 10. The exhaust-gas turbocharger of claim 1, wherein the innerhousing has a wall thickness of less than 1 mm.
 11. The exhaust-gasturbocharger of claim 1, wherein the collar and the edge are coupledwith one another by a material joint.
 12. The exhaust-gas turbochargerof claim 11, wherein the collar and the edge are coupled with oneanother by a radial circumferential weld seam.
 13. The exhaust-gasturbocharger of claim 1, wherein the collar engages behind the edge andis coupled with the edge through thermal joining in a circumferentialjoining zone at a bearing-flange-proximal end of the collar.